Production Plunger

ABSTRACT

A production plunger that automatically reciprocates in a production string of a well to remove formation fluid from the well. The production plunger makes a sealing contact with the production string and includes a passage through which all formation fluid is caused to flow through. The passage includes a valve that operates automatically in response to pressure within the production string to open and close the passage to allow and stop formation fluid from flowing in the passage. The plunger includes a locking device to ensure the plunger does not short cycle and a fail safe mechanism ensuring the valve closes in case of plunger failure, or upon a minimal build up of pressure by shutting in the well. Further, the entire valve is enclosed in the plunger preventing damage to valve elements from impacting downhole equipment, and the plunger includes fluid ports positioned so as not to easily capture well solids.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/672,236, filed Apr. 18, 2005, the entire of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to apparatuses for use in plunger lift operations. More particularly, relating to a plunger that operates automatically in response to pressure.

In general, plunger lift is an artificial-lift method principally used in gas wells to unload formation fluid that has accumulated in the well production string. However, plunger lift can be used in oil wells. An automated system mounted on the wellhead controls the well on an intermittent flow regime. When the well is shut-in, a plunger drops down the production string. When the control system opens the well for production, the plunger and a column of fluid are carried up the tubing string. The surface receiving mechanism detects the plunger when it arrives at surface and, through the control system, prepares for the next cycle.

A liquid loaded well, which is a well having formation fluid accumulated in the production string, experiences reduced production or no production entirely. As such it is desirable to unload the well to increase well production. As such there have been many attempts in providing an apparatus which efficiently unloads a liquid loaded well.

One such apparatus is described in U.S. Pat. No. 4,889,473 to Krueger, which discloses a production plunger including a body having a passage that allows fluid to bypass packer cups carried by the body. A valve in the passageway is held open by a bellows filled with air or an inert gas under pressure. The valve is closed by the pressure of the liquid accumulated above the plunger at which time, gas produced by the well will lift the plunger and the liquid above it to the surface.

While the prior art plungers perform as intended, they include various drawbacks. For example, fluid flows out of the passageway through ports that are upwardly faced. The upwardly faced ports have a tendency to capture and direct debris such as sand or silt into the passageway which results in increased wear on the valve and internal parts as well as potentially plugging the bypass area. Plungers of the prior art have the potential to short cycle resulting in reduced efficiency. In other words, as the prior plungers drop in the well the pressure may cause the valve to close before it is under enough fluid to benefit unloading of the well. Subsequently, as it is lifted to the surface of the well it may open prematurely and cause the plunger to fall back down in the well making it oscillate within the well, never surfacing properly therefore never unloading any fluid or a very small amount. Further, prior art plungers include a fishing neck extending beyond the upper end of the plunger which is formed as part of the valve assembly. As the plunger is lifted, there exists the potential of damage to the valve assembly from the fishing neck impacting the well surface equipment. Also if the plunger is “fished” out of the well with wireline, the jarring action may also damage the valve and internal components, particularly if the plunger is stuck in sand, for example. Moreover, most prior art plungers are not centralized and therefore have the potential to jar within the production string resulting in premature wear to the seal elements and potentially snagging on a casing collar within the well and hanging up the plunger or further damaging the seal elements and potentially creating costly down time to retrieve the plunger.

As such it is desirable to have an improved production plunger which does not have upwardly facing fluid ports, which will not short cycle, which does not include valve assembly elements exposed to damage from impacting well equipment, and which is centralized within the production string, and that fails closed to reduce wireline costs.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved production plunger which overcomes all of the drawbacks of prior devices is provided.

In general, in one aspect, the production plunger includes a body for reciprocating in a production string of a well, the body having a passage extending longitudinally through the body; a valve seat in the passage; a valve seal positioned in the passage; a valve rod connected to the valve seal and extending through the valve seat in the passage; means containing air under pressure connected to the piston and urging the valve seal away from the valve seat; resilient means urging the valve seal towards the valve seat; locking means for releasable engagement with the valve rod to resiliently lock the valve rod in a first position where the valve seal is away from the valve seat and to resiliently lock the valve rod in a second position where the valve seal is in sealing contact with the valve seat; seal means carried by the body for engaging the inner wall of the production string and preventing fluid in the production string from flowing through the production string between the body and the inner wall of the production string; and the body defining a first opening on a first side of the valve seat through which formation fluid can flow into the passage, across the valve seat and out of the passage through a second opening defined by the body on a second side of the valve seat until a quantity of formation fluid is accumulated which is sufficient to compress the air contained by the means for containing air, and to release the locking means from the valve rod to position the valve seal in sealing contact with the valve seat, thereby allowing gas volume and pressure underneath the body to move the body and the accumulated formation fluid to the surface of the well.

There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.

Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 is an axial sectional view of the production plunger constructed in accordance with the principles of the present invention, positioned within a production string and with the valve in an open position;

FIG. 2 is an axial sectional view of the production plunger of in FIG. 1, shown with the valve in a closed position;

FIG. 3 is a transverse sectional view of the production plunger taken along line 3-3 in FIG. 1, showing an arrangement of fluid ports and an upper centralizer; and

FIG. 4 is an enlarged, detailed axial sectional view of the production plunger showing an example of a locking means for resiliently locking the valve in a first open position and a second closed position.

The same reference numerals refer to the same parts throughout the various figures.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and particularly to FIGS. 1-4, a preferred embodiment of the improved production plunger of the present invention is shown and generally designated by the reference numeral 10.

With reference to FIGS. 1-4, the plunger 10 includes a body 12 that can be unitary as shown or made of several joined sections. The body 12 includes a longitudinally extending passage 14 having a top portion 16, a mid portion 18 and a bottom portion 20 all axially aligned.

Seal means 24 are carried by the body 12 for engagement with the inner surface of a production string 26 or the like of a well. In the embodiment shown, the seal means 24 includes two packer cups 24 a and 24 b engaging the inner surface of the production string 26 and preventing formation fluid from passing through the production string between the body 12 and the inner surface, thereby causing all fluid flowing through the production string to be directed through the passage 14.

A valve assembly 28 is entirely positioned in the passage 14 is operable to control fluid flow through the passage. To prevent damage to the valve assembly 28, no valve elements extend beyond the surface of the body 12, as such all of the valve elements are protected from impact with surface or downhole equipment. The valve assembly 28 includes a valve seat 30 which divides the passage 14 into two portions, one on a first side of the valve seat and a second on a second side of the valve seat. A valve seal 32 is positioned approximate the valve seat 30 and is attached to a valve rod 34 that extends through the valve seat and terminates at a collapsible bellows 36, or the like which contains air under pressure. The bellows 36 could reasonably be replaced by any air containment system which is collapsible. A piston 38 may be positioned intermediate of and connected to the valve rod 34 and the bellows 36.

Ports 38 located on the first side of the valve seat 30 extend laterally through wall of the body 12 and connect the annulus 40 below the packer cups 24 a and 24 b to the mid portion 18 of the passage 14. Ports 42, located on the second side of the valve seat 30 extend laterally through the wall of the body 12 and reconnect the annulus 40 above the packer cups 24 a and 24 b to the passage 14 at the top portion 16 thereof allowing fluid from the annulus below the packer cups 24 a and 24 b to flow into annulus above the packer cups when the valve seal 32 is spaced from the valve seat 30 as shown in FIG. 1. The ports 38 and 42 are formed through the body 12 such that the entrance into each port is oriented in a direction that is not upwards towards the surface of the well.

The bellows 36, connected to the valve rod 34 through piston 38 urges the valve seal 32 in a direction away from the valve seat 30 or in other words in a first open position where formation fluid is allowed to flow through the passage 14. The bellows 36, is preferably made of elastomeric material to allow the bellows to expand and collapse under changing pressure conditions in the production string 26, thereby opening and closing the valve assembly 28 respectively. The air pressure within the bellows 36 determines at what pressures within the production string cause the bellows to expand or collapse, as such the air pressure can be adjusted to more precisely control the opening and closing of the valve assembly at predetermined production string pressures. The body 12 can include a passage 23 extending from a side of the body 12 at a lower end thereof through a bottom 22 of the passage into the bottom portion 20, thereby establishing a fluidic coupling between bottom portion of the passage 14 with the well annulus 40.

A resilient element 44, such as a spring is connected to the bellows 36 or piston 38 and urges the valve seal 32 in a direction towards the valve seat 30. If the bellows 36 should leak or otherwise fail, the spring 44 acting on the valve rod 34, will move the valve seal 32 against the valve seat 30, thereby closing the valve assembly 28 and stopping fluid from flowing through the passage 14. The spring force of the spring 44 is not sufficient to collapse the bellows 36 when the bellows is functioning correctly, or in other words, the air pressure within the bellows is greater than the spring force.

To ensure the plunger 10 does not short cycle, a locking means 46 for releasable engagement with the valve rod 34 is provided, best shown in FIG. 4. The locking means 46 releasably engages the valve rod to resiliently lock the valve seal 32 in a first position away from the valve seat 30 or in a second position against the valve seat. Without the locking means 46 a probability exists for the valve assembly 28 to open as the plunger 10 rises in the production string 26 and formation fluid is unloaded. The locking means 46 prevents the premature opening of the valve assembly 28 from occurring. Further, the locking means 46 ensures the plunger 12 falls to a sufficient depth within the production string 26 before the valve assembly 28 is closed. In one example, the locking means 46 could include a least one spring loaded detent 48. It is contemplated that locking means 46 could employ a magnetic catch, or other mechanical locking means to resiliently lock the valve rod 34.

The body 12 includes a top centralizer 50 and a bottom centralizer 52. The top and bottom centralizers 50 and 52 can be attached to the body 12 are formed integrally therewith. The centralizers 50 and 52 prevents the plunger 10 from being “jostled” from side to side in the production string 26 which other wise result in premature wear on the sealing cups 24 a and 24 b. The centralizers 50 and 52 also prevent the body 12 from jarring against the inner surface of the production string 26 and help to ensure better sealing element expansion by keeping the sealing cups 24 a and 24 b centralized within the production string.

A fishing neck 54 can also be provided for use in retrieval of the plunger 10 if for some reason the spring 44 does not close the valve assembly 28, or the seal means are worn beyond usefulness. The fishing neck 54 and be attached to the body 12 at an upper end thereof or can be made integral with the body.

In use, it can now be understood, the plunger 10 with the valve assembly 28 open, as shown in FIG. 1, travels downward in the production string until it reaches a predetermined stop, or falls under enough fluid to cause the valve to close, whichever comes first. As the plunger 10 travels downward in the production string 26, formation fluid in the production string flows through ports 38 into passage 14 from the annulus 40 below the sealing cups 24 a and 24 b and out of ports 42 into the annulus above the sealing cups and accumulates above the plunger. As the formation fluid accumulates an increasing force is applied on the bellows 26 until enough formation fluid is accumulated to collapse the bellows and close the valve assembly 28, as shown in FIG. 2. Gas produced by the well increases pressure in the annulus 40 below the sealing cups 24 a and 24 b. The gas pressure eventually reaches a point that overcomes the pressure of the accumulated formation fluid and the plunger 10 is caused to rise in the production string 26. The formation fluid is unloaded from the production string at the surface as the plunger 10 rises. The formation fluid is unloaded, and the pressure drops until the bellows 36 expands releasing the locking means 46 from the valve rod 34 and opening the valve assembly 28, at which point the plunger 10 falls back downward in the production string 26.

A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims. 

1. A plunger for reciprocating in a production string of a well to unload the well of formation fluid to increase well production, the plunger comprising: a body for reciprocating in a production string of a well, said body having a passage extending longitudinally through said body; a valve seat in said passage; a valve seal positioned in said passage; a valve rod connected to said valve seal and extending through said valve seat in said passage; means containing air under pressure connected to said piston and urging said valve seal away from said valve seat; resilient element urging said valve seal towards said valve seat; locking means for releasable engagement with said valve rod to resiliently lock said valve rod in a first position where said valve seal is away from said valve seat and to resiliently lock said valve rod in a second position where said valve seal is in sealing contact with said valve seat; seal means carried by said body for engaging the inner wall of the production string and preventing fluid in the production string from flowing through the production string between said body and the inner wall of the production string; and said body defining a first opening on a first side of said valve seat through which formation fluid can flow into said passage, across said valve seat and out of said passage through a second opening defined by said body on a second side of said valve seat until a quantity of formation fluid is accumulated which is sufficient to compress the air contained by said means for containing air, and to release said locking means from said valve rod to position said valve seal in sealing contact with said valve seat, thereby allowing gas pressure below said seal means to move said body and the accumulated formation fluid to the surface of the well.
 2. The plunger of claim 1, further comprising: first and second centralizers positioned at opposite ends of said body.
 3. The plunger of claim 1, wherein said first and second openings are defined by said body such the entrance into said first opening and the entrance into said second opening are not facing upward towards the surface of the well.
 4. The plunger of claim 1, further comprising: a retrieval means attached to said body for use in retrieving said body from the production string.
 5. The plunger of claim 5, wherein said retrieval means is a fishing neck.
 6. The plunger of claim 1, wherein said means containing air under pressure is collapsible.
 7. The plunger of claim 6, wherein said means containing air under pressure includes bellows.
 8. The plunger of claim 1, wherein said locking means includes a spring loaded detent.
 9. The plunger of claim 1, wherein said locking means includes a magnet.
 10. The plunger of claim 1, wherein said resilient means is a spring.
 11. A plunger for reciprocating in a production string of a well to unload the well of formation fluid to increase well production, the plunger comprising: a body for reciprocating in a production string of a well, said body having a passage extending longitudinally through said body; a valve seat in said passage; a valve seal positioned in said passage; a valve rod connected to said valve seal and extending through said valve seat in said passage; a piston connected to said valve rod; means containing air under pressure connected to said piston and urging said valve seal away from said valve seat; resilient means connected to said piston and urging said valve seal towards said valve seat; locking means for releasable engagement with said valve rod to resiliently lock said valve rod in a first position where said valve seal is away from said valve seat and to resiliently lock said valve rod in a second position where said valve seal is in sealing contact with said valve seat; seal means carried by said body for engaging the inner wall of the production string and preventing fluid in the production string from flowing through the production string between said body and the inner wall of the production string; and said body defining a first opening on a first side of said valve seat through which formation fluid can flow into said passage, across said valve seat and out of said passage through a second opening defined by said body on a second side of said valve seat until a quantity of formation fluid is accumulated which is sufficient to compress the air contained by said means for containing air, and to release said locking means from said valve rod to position said valve seal in sealing contact with said valve seat, thereby allowing gas pressure below said seal means to move said body and the accumulated formation fluid to the surface of the well.
 12. The plunger of claim 11, further comprising: first and second centralizers positioned at opposite ends of said body.
 13. The plunger of claim 11, wherein said first and second openings are defined by said body such the entrance into said first opening and the entrance into said second opening are not facing upward towards the surface of the well.
 14. The plunger of 11, further comprising: a retrieval means attached to said body for use in retrieving said body from the production string.
 16. The plunger of claim 1, wherein said means containing air under pressure is collapsible.
 17. The plunger of claim 11, wherein said resilient means is a spring.
 18. A plunger for reciprocating in a production string of a well to unload the well of formation fluid to increase well production, the plunger comprising: a body for reciprocating in a production string of a well, said body having a passage extending longitudinally through said body; a valve seat in said passage; a valve seal positioned in said passage; a valve rod connected to said valve seal and extending through said valve seat in said passage; a piston connected to said valve rod; a collapsible means containing air under pressure connected to said piston and urging said valve seal away from said valve seat; resilient means connected to said piston and urging said valve seal towards said valve seat; locking means for releasable engagement with said valve rod to resiliently lock said valve rod in a first position where said valve seal is away from said valve seat and to resiliently lock said valve rod in a second position where said valve seal is in sealing contact with said valve seat; seal means carried by said body for engaging the inner wall of the production string and preventing fluid in the production string from flowing through the production string between said body and the inner wall of the production string; first and second centralizers positioned at opposite ends of said body; a retrieval means attached to said body for use in retrieving said body from the production string; and said body defining a first opening on a first side of said valve seat through which formation fluid can flow into said passage, across said valve seat and out of said passage through a second opening defined by said body on a second side of said valve seat until a quantity of formation fluid is accumulated which is sufficient to compress the air contained by said means for containing air, and to release said locking means from said valve rod to position said valve seal in sealing contact with said valve seat, thereby allowing gas pressure below said seal means to move said body and the accumulated formation fluid to the surface of the well.
 19. The plunger of claim 18, wherein said first and second openings are defined by said body such the entrance into said first opening and the entrance into said second opening are not facing upward towards the surface of the well.
 20. The plunger of claim 18, wherein said locking means includes a spring loaded detent. 